LCD modules are commonly used in a variety of consumer electronics devices including televisions, computer monitors, laptop computers and mobile devices. A typical LCD module can include an LCD cell, backlight and electronics. Many devices including LCD modules can protect the LCD cell by placing a layer of cover glass in front of the LCD module. For cosmetic reasons, it can be advantageous for the cover glass layer to extend to an edge of a front face of the device. Moreover, space limitations can favor designs in which the LCD module and cover glass are as thin as possible, resulting in a reduced overall thickness for the device.
Conventional devices containing LCD modules can leave an air gap between the LCD module and the cover glass layer. There can be several advantages to eliminating this air gap by bonding the LCD cell directly to the cover glass layer. Elimination of the air gap can reduce the thickness of the LCD module, resulting in an overall decreased thickness for the device in which it is contained. Additionally, bonding the LCD cell to the cover glass layer can improve front of screen performance. For example, an image produced by the LCD cell can be brought closer to the front of the device. Furthermore, reflections can be reduced and a likelihood of foreign material or condensation collecting between glass layers can be decreased. However, a mechanical coupling between the LCD cell and cover glass layer can allow stresses imparted on the cover glass to result in unwanted stress on the LCD cell. The LCD cell can operate by selectively rotating an angle of incidence of polarized light as the light passes through two polarizers oriented at 90° to one another. When stress is imparted on liquid crystals within the LCD cell, the angle at which light is rotated as it passes through the liquid crystals can change in a process known as stress induced birefringence. This change in angle can locally increase or decrease an amount of light being emitted by a region of the LCD cell, causing a visible distortion in an image produced by the LCD cell.
When the LCD cell is bonded to the cover glass layer, any stresses imposed on the cover glass layer can be transmitted to the LCD cell, increasing the risk that stress induced birefringence can occur. This can be particularly true when the LCD module is large, such as those used in desktop computers, computer monitors and televisions. Larger devices can weigh more and require the cover glass layer to sustain loads over longer distances. This can increase localized stress on the cover glass layer at points where the cover glass layer is attached to other structures. Moreover, when the cover glass layer is extended to an edge of a device, the cover glass layer itself can become a structural member in the housing of the device, further increasing the likelihood that stress induced birefringence will occur.
Therefore, what is desired is a method for attaching a cover glass layer with a bonded LCD cell to a device housing and backlight assembly while minimizing the amount of localized stress concentrations imparted to the cover glass and LCD cell.